A catheter with two lumens is commonly used in a number of medical situations, such as in treatments of bodily fluids outside the patient. A common example occurs during hemodialysis. A dual lumen catheter is inserted into a large vein, usually the vena cava (by way of the internal jugular vein or the femoral vein) to allow large flows of blood to be withdrawn though one lumen, the aspiration lumen. The blood is then pumped from the aspiration lumen and through the hemodialysis machine where waste products such as creatine and urea are removed. Thereafter the dialyzed or clean blood is fed from the machine into the catheter's second lumen, the infusion lumen, where the blood returns to the vena cava or other vessel.
The lumens in such catheters can occasionally become obstructed, which reduces the flow rate of bodily fluids. The distal tip of the aspiration lumen, for example, may be inadvertently placed against the walls of the vein, which restricts or altogether blocks the flow into the aspiration lumen. Or after a period of time, a fibrin sheath may grow around the distal tip of the catheter. A fibrin sheath is a build-up of cells that encases the catheter and when present, impairs blood flow in and out of the catheter.
Achieving adequate flow is the Achilles heel to extracorporeal treatment of bodily fluids. Hence, it is preferred that the access lines to the body, e.g. catheter lumen(s), remain unobstructed. To this end, some dual lumen catheter designs include holes in the side of the catheter, near the distal end, that open into the aspiration and infusion lumens to increase access and flow. Others split the distal portion of the catheter into two tubes of unequal length, separating the aspiration lumen from the infusion lumen to avoid obstruction. While these designs may combat obstructions, lumen blockage and reduced flows continue to be a problem. The following disclosure further addresses that need.